From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=134.134.136.20; helo=mga02.intel.com; envelope-from=star.zeng@intel.com; receiver=edk2-devel@lists.01.org Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id E43E221E1B75A for ; Sun, 24 Sep 2017 23:19:28 -0700 (PDT) Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 24 Sep 2017 23:22:39 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.42,435,1500966000"; d="scan'208";a="152914160" Received: from fmsmsx107.amr.corp.intel.com ([10.18.124.205]) by orsmga005.jf.intel.com with ESMTP; 24 Sep 2017 23:22:39 -0700 Received: from fmsmsx151.amr.corp.intel.com (10.18.125.4) by fmsmsx107.amr.corp.intel.com (10.18.124.205) with Microsoft SMTP Server (TLS) id 14.3.319.2; Sun, 24 Sep 2017 23:22:38 -0700 Received: from shsmsx104.ccr.corp.intel.com (10.239.4.70) by FMSMSX151.amr.corp.intel.com (10.18.125.4) with Microsoft SMTP Server (TLS) id 14.3.319.2; Sun, 24 Sep 2017 23:22:38 -0700 Received: from shsmsx102.ccr.corp.intel.com ([169.254.2.175]) by SHSMSX104.ccr.corp.intel.com ([169.254.5.152]) with mapi id 14.03.0319.002; Mon, 25 Sep 2017 14:21:40 +0800 From: "Zeng, Star" To: "Wu, Hao A" , "edk2-devel@lists.01.org" CC: "Shi, Steven" , "Fu, Siyuan" , "Ye, Ting" , "Wu, Jiaxin" , "Long, Qin" , "Dong, Eric" , Paolo Bonzini , "Zeng, Star" Thread-Topic: [PATCH v2 4/6] MdeModulePkg/DxeNetLib: Fix negative value left shift Thread-Index: AQHTMqVcnhLqETCovUKlAQo/TF3JH6LFJ7fg Date: Mon, 25 Sep 2017 06:21:39 +0000 Message-ID: <0C09AFA07DD0434D9E2A0C6AEB0483103B9796ED@shsmsx102.ccr.corp.intel.com> References: <20170921064617.2628-1-hao.a.wu@intel.com> <20170921064617.2628-5-hao.a.wu@intel.com> In-Reply-To: <20170921064617.2628-5-hao.a.wu@intel.com> Accept-Language: zh-CN, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.239.127.40] MIME-Version: 1.0 Subject: Re: [PATCH v2 4/6] MdeModulePkg/DxeNetLib: Fix negative value left shift X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 25 Sep 2017 06:19:29 -0000 Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Leave the review to module experts. Thanks, Star -----Original Message----- From: Wu, Hao A=20 Sent: Thursday, September 21, 2017 2:46 PM To: edk2-devel@lists.01.org Cc: Wu, Hao A ; Shi, Steven ; Fu,= Siyuan ; Ye, Ting ; Wu, Jiaxin ; Long, Qin ; Zeng, Star ; Dong, Eric ; Paolo Bonzini Subject: [PATCH v2 4/6] MdeModulePkg/DxeNetLib: Fix negative value left shi= ft REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3D698 Within function NetRandomInitSeed(), left shift a negative value is used in: "~Time.Hour << 24" which involves undefined behavior. Since Time.Hour is of type UINT8 (range from 0 to 23), hence ~Time.Hour wil= l be a negative value (of type int, signed). According to the C11 spec, Section 6.5.7: > 4 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated > bits are filled with zeros. If E1 has an unsigned type, the value > of the result is E1 * 2^E2 , reduced modulo one more than the > maximum value representable in the result type. If E1 has a signed > type and nonnegative value, and E1 * 2^E2 is representable in the > result type, then that is the resulting value; otherwise, the > behavior is undefined. This commit will remove the '~' operator before 'Time.Hour', since it seems= like an implementation choice for generating the seed. Cc: Steven Shi Cc: Fu Siyuan Cc: Ye Ting Cc: Wu Jiaxin Cc: Qin Long Cc: Star Zeng Cc: Eric Dong Cc: Paolo Bonzini Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Hao Wu --- MdeModulePkg/Library/DxeNetLib/DxeNetLib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c b/MdeModulePkg/Libr= ary/DxeNetLib/DxeNetLib.c index 7cd7e3aca0..1ee77fe036 100644 --- a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c +++ b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c @@ -872,7 +872,7 @@ NetRandomInitSeed ( UINT64 MonotonicCount; =20 gRT->GetTime (&Time, NULL); - Seed =3D (~Time.Hour << 24 | Time.Day << 16 | Time.Minute << 8 | Time.Se= cond); + Seed =3D (Time.Hour << 24 | Time.Day << 16 | Time.Minute << 8 |=20 + Time.Second); Seed ^=3D Time.Nanosecond; Seed ^=3D Time.Year << 7; =20 -- 2.12.0.windows.1